The invention relates to a system and method to provide air conditioning in marine environments. While chilled water systems have been used in large commercial buildings and as the standard on very large yachts (over 80 feet), up until now central systems have been the only cost effective solution for cooling of yachts/marine vessels in the range of 45-75 feet, since the cost of chilled water systems has been prohibitive in this size boat. According to the invention it is possible to use modular units to provide chilled water for marine air conditioning, each unit having a cooling capacity of between 16,000-24,000 BTU's so that one unit may be used, or two through four units may be connected together, to effectively (both from the functional standpoint and cost effectively) cool boats in the range of 45-75 feet. The invention is particularly useful for vessels (such as 45 foot boats) which require a 36,000 BTU or greater capacity, with multiple condensing units and air handlers. The chilled water air conditioning system according to the present invention has reduced BTU requirements for the condensing units, no refrigerant line sets, enhanced balanced temperature control throughout the vessel, system energy management, and compressor redundancy to eliminate down time, as well as ease of serviceability.
As with all types of air conditioning systems, BTU load calculations must first be done on any vessel to be air-conditioned to ensure that the equipment selected can provide adequate heating or cooling for all applicable areas. With split central equipment there must be a one for one match of evaporator air handlers to condensing units. In other words, if a vessel requires 62,000 BTU's of air conditioning one must specify 62,000 BTU's of evaporator air handlers and 62,000 BTU's of central condensing. Normally one will have one condensing unit for each evaporator, in some cases one can have smaller evaporators matched to one condensing unit (i.e. one 24,000 BTU condenser can run 2.times.12,000 BTU evaporators).
Chilled water equipment, as according to the invention, has a significant advantage over split central systems in that only the air handlers must equal the calculated BTU heat load for the vessel, whereas the chilled water power plant only needs to accommodate 75-90% of the calculated BTU heat load. In the above example, 62,000 BTU of air handlers only requires 46,500-55,800 BTU's of chiller capacity. The size of the vessel, number of air handlers, and equipment selected determines the percentage of capacity required. Experience indicates that under nominal conditions a chiller plant operates at 50% or less of its capacity because of its automatic energy management feature.
With split central systems one may have only one thermostat control per central condensing unit to control both the condensing unit and the evaporator. Thus, if one has multiple evaporators on one condensing unit, a slave fan speed only control can be used on the slave evaporators, which may not coincide with the end user's preferences. The fan on the second evaporator must always run otherwise, icing can occur resulting in liquid return to the compressor potentially damaging the condensing unit.
With a chilled water system all air handler controls are totally independent from the chiller controls. The chiller has its own energy management system which automatically stages compressors on and off to control water temperature. Each air handler may have individual controls or up to four air handlers can be driven from a single control typically in a large common area. That is, temperature control is totally flexible throughout the vessel.
Installation of split central air conditioning systems requires that an EPA certified technician handle the refrigerant line sets. This is a government regulation imposed to ensure that the R-22 refrigerant used in the system does not escape into the atmosphere. This is a problem for most boat builders as it limits the number of people qualified to install split central equipment in manufacturing. Many boat builders have chosen to contract this work out and as a result can be a logistics problem in manufacturing. Done correctly, the process of attaching refrigerant line sets, evacuating the system, charging the system, finding and repairing leaks in flair fittings and finally balancing the system to ensure the proper refrigerant charge exists for optimum performance is very time consuming and costly for any production boat builder. In reality, due to customer delivery pressures much of this process is rushed, resulting in poor performance of the system in the field often creating warranty and long term reliability problems. Also, because boats, unlike fixed building structures, flex while underway, mechanical refrigerant line set fittings are constantly under stress often resulting in intermittent refrigerant leaks.
Since a chilled water system has a self-contained factory sealed refrigerant system, there are no refrigerant line sets to be installed in the vessel. Therefore, there is no need for an EPA certified technician to perform any installation or system balancing upon startup. The self-contained chiller condensing unit is plumbed to the air handlers via insulated water lines, which is something boat builders are most familiar with. Installing chilled waterlines is as simple as linking a pump, and expansion tank with fill valve, to a closed plumbing loop. Pipe and insulation sizing can be read off of a simple chart and installed by anyone with basic plumbing skills, simplifying the manufacturing process. When the installation is complete, the installer fills the system with fresh water and uses built in air bleeders to purge air from the lines. Then one merely turns on the chiller and sets the air handler thermostats.
Split central systems operate completely independent of one another. This concept has worked well in many applications and gives the end user desired individual climate control, however, there are some drawbacks.
1. Because the thermostats are independent they can easily oppose each other because of air spill over from one area to another. Since each thermostat controls a condensing unit this causes short cycling of compressors leading to premature failure.
2. If a condensing unit fails, there is no redundancy, and the section of the boat which relies on that unit for cooling will not have cooling until the unit is repaired.
3. There is no energy management between the condensing units. They turn on and off independently, and therefore they can be on or off at any given point in time regardless of the total overall heat load on the boat. Only the independent thermostats control the individual compressors.
Although chilled water system air handlers operate independently, they are all tied to the same parallel chilled water loop which is fed back to the chilled water condensing units allowing the compressors to cycle on and off based upon the heat load on the total water loop. Because each air handler is tied into one chilled water loop the total heat load is integrated into one system which is the basis for energy management of the condensing units. The fact that the air handlers are independent allows for desired independent thermostatic control without creating compressor short cycling conditions because the chilled water condensers react to the total balanced load of the chilled water loop.
Each air handler removes heat from the cabin space and transfers the heat into the cold chilled water loop. As air handlers turn on and off, the average temperature returning in the closed loop to the chiller condensers rises or falls. The chiller condensing system senses the temperature of the water and turns compressors on and off based upon the overall total heat load of the boat. The change in temperature of the water is very gradual since the volume of water contains stored energy, which acts as an energy buffer. This gradual change eliminates short cycling of the compressors therefore increasing the useful life of the system and eliminates those initial cold blasts of air associated with typical direct expansion start-ups.
The chilled water condensers only need enough capacity for 75-90% of the total heat load calculations of the boat. Since heat load calculations are typically based on high ambient worst case conditions, the only time full capacity is needed is for a warm start up. Under normal operation, 50% of the total cooling capacity is usually more than enough to remove heat from all areas of the boat. This is why 75-90% downsizing of chilled water condensers as compared to total worst case heat load requirements is practical in all applications.
Chilled water systems normally comprise two or more modular condensing units (hence the 36,000 BTU minimum discussed above) which have independent sealed compressor systems creating complete operational redundancy. This means that if a chilled water condensing unit malfunctions for any reason the other operating condensing unit(s) will continue to remove heat from the chilled water loop, which provides cooling to the entire vessel. Since 50% capacity is normally all that is required of a system operating in nominal conditions, the end user has time to facilitate repairs without being inconvenienced.
Mechanical breakdowns in a split central system require an EPA certified technician to troubleshoot and repair the system. In case of compressor's failure, the entire system needs to be evacuated and removed for replacement or repair. During this process the end user may be seriously inconvenienced as discussed above. Upon replacement, the entire sealed system must be evacuated, recharged and balanced for proper operation. This can be a costly and time-consuming process, not to mention the possibility of a poor flare fitting or a loose flare.
Since a chilled water system has redundant components, a component or compressor failure rarely results in inconvenience to the end user. Although some repairs will require an EPA certified technician, the end user can choose to remove the selfcontained sealed unit and replace it in a matter of hours or send it to an authorized service center for repairs. Removal of a modular chilled water condensing unit simply requires disconnecting and capping off the water lines and disconnecting the electrical supply. Installation of the new or repaired unit requires connecting water lines, bleeding out the air and reconnecting the electricity.
The location of the modular condensing unit according to the invention should be dry and accessible for service. The condensing unit should be secured to a level horizontal surface with brackets. The brackets hold the weight of the equipment as well as handle any torsional movement. Each condensing unit must be independently supported, not stacked directly on top of each other.
Also according to the invention reinforced marine grade hose is to be used for the seawater circuit. The hose is to be routed upwards from the thru-hull intake to the condensing unit to prevent air locks in the centrifugal seawater pump. Circulation connections between the condensing unit and chilled water lines are to be made with properly sized fittings and reinforced marine grade hose. All hose connections are to be double clamped. Ball valves should be installed at chilled water inlet/outlet of each unit and each air handler for overall serviceability of system. All hose and fittings should be properly insulated upon completion of leak tests to prevent condensation and energy or capacity loss. The condensing unit chassis for each modular unit has an integral condensation drain pan for removal of any water that may form. A hose should be secured to this drain pan spud and routed downward to a proper sump or overboard discharge outlet.
The air conditioner air handler is never installed in bilge or engine room areas. It is important to insure that the selected location is sealed from direct access to bilge and/or engine room vapors. Condensate drain lines should not be terminated within four feet of any outlet of engine or generator exhaust systems, nor in a compartment housing an engine or generator, nor in a bilge (vapors can travel up the drain line), unless the drain is connected properly to a sealed condensate or shower sump pump. Failure to comply may allow bilge or engine room vapors to mix with the air conditioners return air and contaminate living areas.
All circuit breakers and wire gauge must be sized according to marine design standards. Only stranded tinned copper wire should be used. All wiring should be routed through strain-relief connectors provided in the electrical boxes.
All equipment should be properly grounded using grounding lugs provided on each unit's chassis. Electrical boxes are pre-wired for power and control circuits. Mechanical control panels can be remote mounted in a convenient location, using four mounting screws. Field wiring is required between remote switch and unit electrical box.
All chilled water condensing units according to the invention use closed-refrigerant circuits, precharged with R-22 refrigerant, hermetically sealed, and factory tested and certified. No additional refrigerant is required during the installation or at initial start-up and operation of the system. In keeping with regulations set forth by the EPA, only certified technicians should perform service on, or make adjustments to, any refrigerant circuit.
The system according to the invention functions as follows: During the off-peak requirement times a single compressor would handle the air conditioning load on its own, and only requires a second compressor to kick in if the first is not able to adequately chill the water based upon the ambient temperature. This is important especially in relation to shore power and/or generation on-board. With current competitive systems, due to the fact that the compressors cycle together, they require a much larger power draw and one might have to run a generator overnight to meet the electrical demand. Not only is this a noise pollution problem, but also the carbon monoxide produced from the exhaust to the generator is a potential life hazard. With the system of the invention, since a single compressor will handle the load in the off-peak times (i.e. late evening, overnight, early morning), there is no need for additional power other than the typical shore power hook-up (30 amp). One benefit of this is that the boater uses the power he/she paid for with the docking, instead of the fuel for the generator. It should also be noted that in order to achieve long life of the system components, the compressors may be programmed to cycle/run in "rotation" so that the same compressor is not the one running each time a single compressor handles the load.
The installation of the modular units of the invention, each of which is basically a "shoebox" which looks very simple and nondescript, requires substantially only hook-up of power and four hoses (two saltwater (intake and discharge) and two for fresh water feed and return lines to the air handlers). In addition, the control panel/unit is preferably completely solid state for ease of use, and operation.
The modular units according to the invention may be provided in a plurality of sizes. For example there may be three sizes, 16,000 BTU/H, 20,000 BTU/H, and 24,000 BTU/H (cooling capacity). The 24,000 BTU/H units may use scroll compressors, while the other units use rotary compressors. The condenser coil may be constructed of spiral fluted cupronickel to provide maximum heat transfer and high corrosion resistance. The 16,000 BTU/H units typically have a depth of between 17-19 inches (e.g. about 18 inches), a width of about 10-13 inches (e.g. about 111/2 inches) and a height of between about 10-13 inches (e.g. about 11.25 inches). The 20,000 BTU/H units have the same depth and width but with a height of between about 12-15 inches (e.g. about 13.5 inches). The 24,000 BTU/H units may have the same depth but a width of between about 12-14 inches (e.g. about 13 inches) and a height of between about 14-17 inches (e.g. about 15.75 inches).
According to one aspect of the present invention a marine vessel (such as a yacht or other boat) with a chilled water air conditioning system is provided comprising: A marine vessel in the range of 45-75 feet, and including a plurality of different areas to be air conditioned and having a predetermined high ambient worst case conditions cooling capacity. An air handler, including a coil unit and a blower, associated with each of at least some of the different areas. Between two-four water-chilling modular units for cooling water and circulating the cooled water to the air handler coil units, the modular units each having a condenser coil and the units collectively having a condenser cooling capacity between about 75-90% of the predetermined cooling capacity. And a chilled water pump and expansion tank unit operatively connected to the water-chilling modular units.
The system according to the invention also includes the following aspects: The water chilling modular units each comprise a compressor, an evaporator coil, a reversing valve, and expansion tubing in addition to the condenser coil. The condenser coil, compressor, reversing valve, evaporator coil, and expansion tubing are disposed within substantially the same casing, and are mounted on a drain pan. Four hose connections are provided for the casing, two of the hose connections are operatively connected to the condenser coil and connected by a hose to a seawater pump and an overboard discharge of the marine vessel, and two of the connections are operatively connected to the chilled water pump and an air handler coil unit. Solid state electronics for operating the modular units are provided so that which of the plurality of units is running at any point in time when less than full capacity of the collective units is necessary is rotated. Each of the units preferably has a capacity of about 16,000 BTU's per hour, about 20,000 BTU's per hour, or about 24,000 BTU's per hour. Each of the units preferably has a depth of between about 17-19 inches, a width between about 10-14 inches, and a height of between about 10-17 inches. The solid state electronics preferably comprises freeze-stat protection and an associated sensor, a solid state control with a digital readout providing temperature and diagnostic information and as inputs a high refrigerant pressure switch, a chilled water flow switch, and a return water sensor.
According to another aspect of the present invention a water-chilling modular unit for air conditioning a marine vessel is provided. The unit comprises: The casing having a power line extending therefrom and a plurality of water transporting hose connections in the exterior thereof, the casing being devoid of any refrigerant lines extending in or out thereof. A compressor, condenser coil, evaporator coil, reversing valve, and expansion tubing provided within the casing, including refrigerant lines extending therebetween. Two of the water transporting connections operatively connected to the condenser coil, and two of the connections operatively connected to the evaporator coil, the evaporator coil circulating chilled water therein and chilling the water circulating therein.
The water-chilling unit according to the invention also includes: A casing is mounted on a drain pan to receive condensate from components within the casing. Each of the units has a capacity of about 16,000 BTU's per hour, about 20,000 BTU's per hour, or about 24,000 BTU's per hour. Each of the units has a depth of between about 17-19 inches, a width between about 10-14 inches, and a height of between about 10-17 inches. A high refrigerant pressure switch is preferably operatively connected to a refrigerant line between the compressor and the reversing valve. Pumps for circulating water through the water transporting connections are mounted exteriorly of the casing, and there is no water circulating pump mounted interior of the casing. A solid state control mounted exteriorly of the casing includes freeze-stat protection and a supply water temperature monitor, and a digital readout providing temperature and diagnostic information.
According to yet another aspect of the present invention there is provided a method of air conditioning a marine vessel (such as a yacht or other boat) in the range of 45-75 feet and including a plurality of different areas to be air conditioned and having a predetermined high ambient worst conditions cooling capacity, using a chilled water air conditioning system and an air handler, including a coil unit and a blower, associated with each of at least some of the different areas to be air conditioned. The method comprises: (a) Connecting between two-four water chilling modular units for cooling water and circulating the cooled water to the air handler coil units, each modular unit including a condenser coil and an evaporator coil within the marine vessel, the modular units having collectively a condenser cooling capacity between about 75-90% of the predetermined cooling capacity; and (b) circulating substantially ambient water from exteriorly of the marine vessel to the condenser coil and ultimately discharging the circulated water from the condensing coil to the exterior of the vessel.
In the method preferably (a) is practiced utilizing water-chilling modular units each having a cooling capacity of between about 16,000-24,000 BTU's, and the method further comprises operating less than all of the water-chilling modular units during low cooling load conditions while operating at least one of the water-chilling modular units, and rotating which of the water-chilling modular units are operated or not operated during low cooling load conditions.
It is the primary object of the present invention to effect air conditioning of a marine vessel, particularly in the 45-75 foot size, utilizing a chilled-water system, which is advantageous compared to conventional split central systems. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.